linux-kernel - Re: [PATCH] ACPI/PCI: fix array

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Date:   Sat, 18 Jul 2020 07:27:38 -0700
From:   Joe Perches <joe@...ches.com>
To:     kernel test robot <lkp@...el.com>,
        sathyanarayanan.kuppuswamy@...ux.intel.com, bhelgaas@...gle.com
Cc:     kbuild-all@...ts.01.org, linux-pci@...r.kernel.org,
        linux-kernel@...r.kernel.org, ashok.raj@...el.com
Subject: Re: [PATCH] ACPI/PCI: fix array_size.cocci warnings

On Sat, 2020-07-18 at 16:01 +0800, kernel test robot wrote:
> From: kernel test robot <lkp@...el.com>
> 
> drivers/acpi/pci_root.c:150:37-38: WARNING: Use ARRAY_SIZE
> 
>  Use ARRAY_SIZE instead of dividing sizeof array with sizeof an element
[]
>  static char *get_osc_desc(u32 bit)
>  {
> -	int len = sizeof(pci_osc_control_bit) / sizeof(pci_osc_control_bit[0]);
> +	int len = ARRAY_SIZE(pci_osc_control_bit);
>  	int i = 0;
>  
>  	for (i = 0; i <len; i++)

And likely better to not declare len at all
and ARRAY_SIZE directly instead.

static char *get_osc_desc(u32 bit)
{
	int i;

	for (i = 0; i < ARRAY_SIZE(pci_osc_control_bit); i++) {
		if (bit == pci_osc_control_bit[i].bit)
			return pci_osc_control_bit[i].desc;
	}

	return NULL;
}

and also likely both arrays should be const.

Something like:
---
 drivers/acpi/pci_root.c | 17 +++++++++--------
 1 file changed, 9 insertions(+), 8 deletions(-)

diff --git a/drivers/acpi/pci_root.c b/drivers/acpi/pci_root.c
index f90e841c59f5..bfb437cf749a 100644
--- a/drivers/acpi/pci_root.c
+++ b/drivers/acpi/pci_root.c
@@ -122,10 +122,10 @@ static acpi_status try_get_root_bridge_busnr(acpi_handle handle,
 
 struct pci_osc_bit_struct {
 	u32 bit;
-	char *desc;
+	const char *desc;
 };
 
-static struct pci_osc_bit_struct pci_osc_support_bit[] = {
+static const struct pci_osc_bit_struct pci_osc_support_bit[] = {
 	{ OSC_PCI_EXT_CONFIG_SUPPORT, "ExtendedConfig" },
 	{ OSC_PCI_ASPM_SUPPORT, "ASPM" },
 	{ OSC_PCI_CLOCK_PM_SUPPORT, "ClockPM" },
@@ -135,7 +135,7 @@ static struct pci_osc_bit_struct pci_osc_support_bit[] = {
 	{ OSC_PCI_HPX_TYPE_3_SUPPORT, "HPX-Type3" },
 };
 
-static struct pci_osc_bit_struct pci_osc_control_bit[] = {
+static const struct pci_osc_bit_struct pci_osc_control_bit[] = {
 	{ OSC_PCI_EXPRESS_NATIVE_HP_CONTROL, "PCIeHotplug" },
 	{ OSC_PCI_SHPC_NATIVE_HP_CONTROL, "SHPCHotplug" },
 	{ OSC_PCI_EXPRESS_PME_CONTROL, "PME" },
@@ -146,17 +146,18 @@ static struct pci_osc_bit_struct pci_osc_control_bit[] = {
 };
 
 static void decode_osc_bits(struct acpi_pci_root *root, char *msg, u32 word,
-			    struct pci_osc_bit_struct *table, int size)
+			    const struct pci_osc_bit_struct *table, int size)
 {
 	char buf[80];
 	int i, len = 0;
-	struct pci_osc_bit_struct *entry;
 
 	buf[0] = '\0';
-	for (i = 0, entry = table; i < size; i++, entry++)
-		if (word & entry->bit)
+	for (i = 0; i < size; i++) {
+		if (word & table->bit)
 			len += scnprintf(buf + len, sizeof(buf) - len, "%s%s",
-					len ? " " : "", entry->desc);
+					len ? " " : "", table->desc);
+		table++;
+	}
 
 	dev_info(&root->device->dev, "_OSC: %s [%s]\n", msg, buf);
 }